


And Now, Some Butt

by acheeseball



Series: the x-reader THREE-parter haha [3]
Category: Undertale (Video Game)
Genre: ???? - Freeform, Anal Fingering, Anal Sex, Banter, Dating, Established Relationship, Exhibitionism, Gen, Rimming, Strap-Ons, Vaginal Fingering, and alphys being alphys, mettatons butthole, mettatons gotdam butthole
Language: English
Status: Completed
Published: 2017-01-20
Updated: 2017-04-11
Packaged: 2018-09-18 18:21:38
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 8,206
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9397394
Author URL: https://archiveofourown.org/users/acheeseball/pseuds/acheeseball
Summary: what can I say, you got mettaton, you got butts, you got a kinky reader. And it all started after a bunch of lengthy repairs and an upgrade to a *certain* part of mett's body. guys this is a pegging fic ok





	1. just like in the animes

**Author's Note:**

> whoa!!!! cheesy is back??? how can be???? and the answer is i have a deep psychological attachment to a pixel robot, driving me to write porn to express my Unending Love for him. love ya mettaton.
> 
> yeah I know last time i said i would do a mettacest fic and i still miiiiight except i had a thought and i was like "damn i wont die a man until i have written mettaton x reader x pegging" so here we are, adding a third installment to my reader insert series
> 
> you dont have to read from the beginning unless u want tho I MEAN WHO HAS TIME FOR METTATON PORN IN THE YEAR OF OUR LORD 2017 OH YEAH THATS RIGHT
> 
> me
> 
> pls enjoy whoever is still a robot fucker

Sure, it was a hassle waking up early and coming all the way down to Hotland from the surface. Yes, it was frustrating when you set foot in that hellish lava pit and immediately made sweat rags out of every piece of cloth on your body. The soles of your shoes may have softened with every step on the scalding ground, your throat may have been desiccated from the first breath of soupy air, but dammit, these were the obligations of a relationship. One absolutely needed to brave the absurd conditions on this side of the underground in order to see one’s robot lover after three days of him being worktable-ridden with heavy upgrades.

All you knew, really, was that Mettaton would be a bit weak for a few days after the upgrades, so as a post-op celebration date, you two had agreed to see a movie as soon as he was ready to move around again. Nothing that special, but it didn’t matter to you, since you’d get to spend precious time with him. You could’ve gone on a date to the DMV for all you cared.

You coughed dryly, walking as fast as you could to Alphys’s lab once it was in sight. There was a small doorbell off to the left side of the giant industrial doors, and you jabbed it quickly with your sleeve over your hand. It was better than burning your skin on the metal.

After a grueling 10 seconds, the doors slid open with a mechanical hiss, revealing the reptilian scientist along with a blast of slightly-cooler air.

“O-oh!” Alphys squeaked as soon as she noticed your miserable state. She clasped your hand, tugging you inside hurriedly. “I-I-I’m so sorry there isn’t an easier way for you to get down here without being scorched. M-maybe I could build some s-sort of tunnel, or--”

“Nah, you don’t have to go to all that trouble,” you assured lightly. “I can deal with it.”

Alphys looked at you quizzically as you fanned yourself with your shirt collar. You remembered a bottle of water sitting in your bag, and fumbled for that with your other hand. “So, he’s finally done, right?”

“Oh, yeah!” said Alphys, turning towards the lab’s escalators. “Mettaton’s upstairs getting his stuff together before he leaves. He’s p-pretty happy to finally be able to get around again! He w-wouldn’t stop talking about you and he was always whining for me to bring him more magazines.”

“MTT Monthly?”

“What do you think.”

You rolled your eyes while taking a sip of water. Alphys started for the escalators with you following behind.

“So what exactly got updated?” you questioned. Before Mettaton had undergone the equivalent of a 72-hour surgery (with breaks), he had given you a scattered rundown of what was Alphys would tweak, and what she would all-out replace. He didn’t seem that eager to undergo the long procedure, as he usually wasn’t when he was faced with long maintenance sessions. This time around, though, you could tell there was this weird underlying excitement, and you couldn’t figure out why. He would quickly cover it up with a dramatic wail of apology to his absent fans for his eventual disappearance.

“Um, let’s see, it was quite a lot.” Alphys tapped her claws against her chin. “First there was one of his core processors, that was in desperate need of replacement… hm, a-and some adjustments to his balance mechanisms, his digit functionality, and a slight retouching on his chassis…”

She spouted a bunch of specific jargon, mostly to herself, as if she were making sure she had done absolutely everything. You continued to frustrate over why Mettaton would be the least bit up for any part of this.

“Didn’t Mett say you’d be needing a lot more synthetic skin for this one?”

Back when he’d said that, you’d assumed that meant that the other side of his face would finally get finished, but judging by Alphys’s following expression, that couldn’t have been the case. She was reddening way too much for this to have been something that innocuous.

“Well, i-it’s true I-I did end up using a lot of skin grafts,” she admitted. She looked like she wished she hadn’t said anything at all. You raised an eyebrow.

“Skin grafts for what in particular?”

Alphys made a noise like a suffocating canary and darted her eyes around the room. “I-I-I think you’d better a-ask him when you see him.”

Before you could respond, Alphys scurried away to another room, murmuring about checking something on her computer. You stood for a second, confused and suspicious, then decided to head up the escalators where Mettaton would be waiting.

You allowed yourself a small grin once you stepped on. Surely one he saw you he’d shower you in kisses and trap you in a robotic bear hug. At least, you hoped so. Surely Alphys wouldn’t have let him off the hook if he was too weak to even manage being affectionate. You made sure you would ask him about his limits.

“UGH, you’re kidding me.”

You were about halfway up when Mettaton’s frustrated voice reached your ears. Eagerly, you skipped steps to get to the next floor faster. You wondered if you’d be able to tell that any work had been done.

“Come ONNNN.”

You heard him grumble among the sound of random objects being moved around the floor. You reached the top of the escalator and stepped off, but you were glad you hadn’t given him a passing glance, or your double take would’ve made you trip and break something.

He was kneeling under the worktable and rummaging around for something through an obscene clutter of tools and other items. Although, that was hardly the focal point of what you were looking at, since for some reason, he had decided to do this without any pants on.

It wasn’t like seeing a flash of his genitals was a new thing for you, but you never recalled him having an asshole.

One part of you was dumbfounded, and the other part was actually, shamelessly, archiving the image before you for certain fantasy purposes. That lasted for two seconds before you mentally slapped yourself. What the fuck.

It was for sure an asshole.

For lack of a better word, all that came out of your gaping mouth was a heavy “Uh.”

Mettaton’s head collided violently with the bottom of the table, and he yelled even more. He scuttled around the floor, trying and failing to regain dignity. Finally, he settled for staring at you pitifully while cupping his crotch.

“I didn’t hear you come up,” he peeped.

It wasn’t like you could pretend you hadn’t seen it, because you had definitely seen it. He knew it, too. You thought of the underlying excitement he’d had before the upgrades, and Alphys’s earlier blushfest.

So either this was kinky or Mettaton was 100% up for the full human digestive system experience. Oh god, don’t think about a combination of both.

The robot proved to be cornered and could say nothing in his defense. Instead he rose to his feet, heels clicking loudly, and snatched his leggings from the table to yank them on.

“Mett, I have questions.”

“Darling, darling,” he piped up, trying not to trip on his own feet, “I’m so glad to see your lovely face again! I was just looking for my keys since I dropped them under the table.”

“Ok, I get that, but is there any particular reason you were waving your new asshole around while you were at it?”

He pretended not to hear you and smoothed out his leggings primly. “And I also thought I’d point out that we’re going to be late to the movie.”

Not only was that an obvious swerve around the subject at hand, but it turned out to be true. You whipped around to look at the large wall clock near the atrium of the lab and noticed you had less than five minutes to get there. Your heart sank a little. His first day out of the lab, and it was already going wrong.

You grumbled, then turned back to him. “You’re lucky all I want to do is go on a date right now. Questions later.”

“Oh, marvelous.” Mettaton scooped up his bag from the table, then bent down to kiss you jovially. He parted, and both of you jogged down the escalators. “Let’s get a move on. And I hope you can forgive me, that wasn’t my proudest moment.”

“I didn’t know you felt shame,” you remarked. Mettaton was about to reply when Alphys’s voice came burbling from the room she had disappeared to.

“Oh, a-are you two leaving?”

“Yeah, we’re late!” You said. “But thanks for fixing Mett!”

“Y-y-you’re welcome?” Alphys spluttered. “H-hope you can make it to the movie on time, though!”

“See you later, Alphy!” Mettaton sang. You flipped the switch to the lab’s doors, and were promptly reunited with your old enemy, Hotland’s heat. It was a good thing that 1; Mettaton offered to carry you, and 2; the man could run in heels. You were in your car and on the way to the theater in no time.

Maybe it was your skepticism of Rotten Tomatoes talking, but no matter how good the movie turned out to be, all you saw yourself thinking about in the meantime was just what was Mettaton planning to do with a goddamn robotic rectum.


	2. theater and chill??

**Notes for the Chapter:**

> boink dontcha love the month-long waits between updates

One would think that on the way to the theater, you would’ve been able to interrogate him on what you had just seen, but Mettaton continued to dance around the subject with a crank at the volume dial on your radio. You gave up for the time being, and upon reaching the theater, you both threw on some hasty “disguises” in a cheap attempt at some anonymity while you were out in public. You figured your sunglasses and uncharacteristic hair bun were enough to blend in, but any idiot could pick out a six-foot clunking behemoth with shades, a pink beanie, and some sort of designer poncho in a crowd. Not that it was a big deal; you weren’t in an especially crowded area so you might be allowed some space despite everyone knowing it was the robot star and his human sweetheart, out and about once again. 

When the tickets had been bought, he and you rushed into the movie, which had already started without you. Settling for a seat in the very back, you kicked back with a sigh and tried to pay attention.

Tried.

Honestly, the sensible thing to do would have been to sit down, shut up, enjoy your robot boyfriend’s company, and try to invest yourself in the humorous yet inspiring drama-comedy neo-romance/action-horror (whatever this genre was) playing in front of you. This movie wasn’t even about him, and  _ Mettaton  _ seemed invested.

But of course. Your imagination  _ haaaad  _ to go there.

Soon enough you tuned the movie out almost completely. Such is the power of your mind when it fixates on the increasingly tempting prospect of  _ oh my god you wanted to peg him. _

Despite how honest you were with each other concerning sex, for some reason you had always been too shy to ask to play a more dominant role. That wasn’t to say you couldn’t ever take a bit of control and make him beg for your touch, but though you had considered it many times, you hesitated to tell him you wanted to be on top for a try. Now he had not one, but two possible ways of entry.

Well, no going back now. That had to be the reason he had gotten it, so you let go of any inhibitors to your imagination. Now your thoughts drifted to how well-shaped his ass was. For the love of god.

You had no qualms about spanking and pinching it when things got heated, and you decided that now you definitely wouldn’t have any qualms about asking to give him a rimjob. Oh, man. Usually you didn’t care for that sort of thing, but everything about Mettaton was built for aesthetic, or movement, or pleasure. So yes, you supposed what you wanted right this second was to bury your face in his ass, and then fuck him as senselessly as he always fucked you.

As you were having your little daydream, a metallic grunt brought you back to earth. Mettaton was leaning towards you, and the white glow of the movie screen outlined his silhouetted features. 

“You know, this movie was good at first, but they could have at least had more montages with my songs in them. Anywho, you look like you’ve been deep in thought for some time. What’s in your pretty little head right now?”

Before you could give away that you’d been having a gross fantasy, you answered his question with one of your own. “So, what made you want an asshole?”

Mettaton snorted uncharacteristically and shook his head, surely realizing how absurd the situation was. “I think you know the reason.”

“Do I?” You hoped to god he was thinking exactly what you were thinking.

“Well, for one thing, it makes me feel pretty human to have a full set of genitals,” he said with a weird kind of glee. “Even if, you know, sex isn’t really what an anus is for, but if that never stopped humans, then why should it stop me?”

“So it’s definitely not for an artificial digestive system.”

“ _ Heavens _ no,” Mettaton grimaced. “I value being fucked in the ass over the ability to process food.”

You were about to wholeheartedly concur, but he quickly added, “i-if you feel comfortable doing that to me. There’s always the infinitesimal possibility that what I’ve gathered from your fascination with my orifices could be wrong, but I doubt it.”

“Hey, if anyone knows what I can do beyond missionary, it’s you,” you said, smirking. “God, I wanna do so many things to you.”

There came an angry shush from a few rows in front of you, and you wanted to die immediately. Mettaton tried to muffle his laughter in his hands. He lowered his voice to a whisper.

“That can surely be arranged, darling.” Warm lips pressed against your temple, then your cheek. Your heartbeat picked up a fluttering tempo. “In fact, I want to do it today.”

A hazy veil of love and lust was settling over you, but through that you felt concern. “Wait, are you sure? I don’t wanna hurt you if you’re still sensitive from all those upgrades.”

Mettaton smiled against your skin. “Don’t worry, I’ll tell you if anything feels wrong. I doubt the masochist in me will give it away that easily, though.”

“Damn, you’re gonna totally wreck yourself one day,” you chided. Mettaton moved closer to you, his hands advancing over your shoulders, tickling the nape of your neck. As you began to make out languidly, the desire for the night ahead seared underneath your skin. The robot’s hot mouth only tempted you more.

As if he could sense this, he passed his tongue slowly over your lower lip, and drew back with a knowing look. “I know you must not want to wait until tonight, but unfortunately after the movie I have to hold an emergency meeting over at my hotel so  _ some  _ employees can gain a more thorough understanding of what customer service means.”

You pitied whoever was doomed to suffer his wrath. But more importantly, your clit practically fucking hung its head in disappointment. So much for ditching the mediocre movie in favor of another sexcapade.  _ Come on, _ you told yourself,  _ you’re not a damn baby, you can wait. _

_ “ _ How long do you think it’ll take?” you asked.

“I’d say it would take up the whole afternoon,” he said innocently. “I don’t think I’d be free until the evening.”

You squinted at him. “Liar.”

“Sounds like you’re just impatient and horny,” Mettaton said derisively. “Though, I can’t blame you. It’s no shocker that you’re practically drooling at the thought of rutting me into the bed.” His hands shifted position, now curling around your waist. “Dear me, you must be aching down there.”

Down where. Oh.  _ Oh.  _ His hands reached your hips. There, his gloved thumbs tucked themselves primly underneath the waistband of your jeans.

“In the  _ fucking  _ movie theater, Mett?”

“Yes, in the  _ fucking  _ movie theater, all the way in the back where no one will be the wiser.” Somehow his talented fingers undid your button with a single flick. You sucked in your breath.

“Well, that is,” he continued, “unless you start making noise.”

You didn’t make an effort to stop him, and in fact you thrusted into his touch when he wordlessly slipped his hand into your pants, feeling you up through your underwear. You shivered and leaned your head back. You couldn’t believe you were letting him do this.

“Oh, that’s adorable,” he cooed loftily, digging a finger into your entrance. “Soaked already.”

“Hah, yeah…” Already, some indulgent sounds were slipping out. Biting your lip was the only way to silence yourself. Looking over at him as he began to knead at your clit, you made out the curve of his lewd grin and driven gaze. It wasn’t often he got this far with you in public, and surely it was sending him into a frenzy, thinking about all the clueless people in here and watching you stifle your moans.

He continued, rubbing you in all the right places even through his gloves and your panties, and you thought you might come soon. You should have expected it, but with a mean-spirited chuckle, he slipped his hand back out of your pants after a few minutes, interrupting your plateau of pleasure. Typical. You gritted your teeth as he removed the glove that had touched you, and stuffed it into his bag. Hmm, what was he gonna do with that, you wondered.

“Did you think I was going to let you come, and ruin all the anticipation for tonight?” His smug tone annoyed you, but you supposed he had a point. The dopamine running through your body hadn’t given you a chance to consider. Still, you knew he knew exactly what he was doing. Mettaton was a master at teasing you into agony.

“You’re an asshole,” you said without thinking.

“No, I just have one.” He delighted in your defeated look. You made sure you’d make him pay the minute you got your hands on a strap-on.

On account of the movie’s dwindling quality, you both considered leaving to go shopping or to some other place until it was time for his meeting. To your dismay, though, a battle scene with one of Mettaton’s proudest songs suddenly exploded onscreen, instantly transfixing him. And wouldn’t you know it, this happened to be the part where the character development picked back up. There was no choice but to stay until the end.

Once out of the theater and back in the car, you gave him a lift over to his resort. When you arrived, you stopped near the front entrance, and Mettaton pecked you on the cheek before stepping out.

“I’ll text you when I’ve wrapped this up,” he said. Pursing his lips, he cracked his knuckles, and you wondered why that was even possible. “Pray for me, honey.”

“That’ll be as holy as I get today,” you quipped.

“Indeed.” Mettaton squinted slyly and gave you a quick wave before strutting on inside.

You sighed wearily and figured you might as well sit around at home for the rest of the day. After all, it might be for the best. Topping someone would probably require a lot of energy. As you drove, you shook your head incredulously for the umpteenth time at this whole situation. You were going to count the hours until it was time.

  
  


**Notes for the Chapter:**

> hey hey you know what mtt probably wore it was probably this: https://www.powdercashmere.com/wp-content/uploads/2015/05/Button_Poncho_LilyPink_1.jpg


	3. fucc .

**Notes for the Chapter:**

> wazzup boisss this sex scene was 11 pages long and i no longer deserve to be part of the human race
> 
> at least the wait for this chapter didnt come up to two months tho >:^7

You didn’t own any strap-ons. That honor belonged to Mettaton. You thought about texting him for clarification on what exactly the plan was for tonight, but you decided you’d better not interrupt whatever he was doing and let him text you first like he had promised. 

In the meantime, you carefully planned a nap so you wouldn’t wake up groggy, and then followed it with a long, hot shower. You felt proud of yourself for being so...diligent??

As you snacked on some granola to keep your hunger at bay, your phone buzzed. You smirked at the screen when you saw the text from Mettaton.

Unlocking your phone, you read the message:

_ I’m done for the day! Btw, you’ll have to meet me at Alphys’ lab. ^^ _

You pursed your lips, not expecting this.

_ lol you sure? do you have a room in her lab or what,  _ you tapped out.

_ Yes, and it’s close by to where I am, so it’s more convenient ;) _

You leered at the screen.

_ lazyass -_- ,  _ you responded.

_ Excuse me!! If you keep calling names you’re not getting my ass, lazy or not >:( _

You probably walked into that one. You watched as he typed another message.

_ Plus, I have just what we need over at the lab~ you won’t need to bring anything but your pretty self ;) _

He was going to wear out that winking emoji. All cynical thoughts aside, though, you felt a slight blush creep across your cheeks as you realized just how soon you’d be doing this. Your skin buzzed with a latent anticipation.

_ When should I meet you there?  _ You typed.

_ Around 6-6:30 should be alright~   _ Mettaton replied.  _ Oh, and be sure to text me when you get there and wait for me to let you in, alright? _

An odd request, but you made sure to remember it. You still had some getting ready to do, so this left you a reasonable amount of time. You finished off your granola, then headed off to get dressed, texting as you walked.

_ Cool,  _ you said.  _ Hope youre ready for me to dom you until you cant even speak. _

After sending that, you immediately shut off your phone in embarrassment. Teasing didn’t tend to be your strong suit.

-

Thank god the perpetual sauna called Hotland tended to cool to bearable levels in the evening. It was too early to be getting sweaty just yet. The length of the trip didn’t bother you so much this time around, seeing as you were too preoccupied with what was in store. 

Now, you stood before the towering lab doors for the second time that day. Your finger hovered over the doorbell, but you suddenly remembered what Mettaton had said, and instead pulled out your phone to text him.

_ Hey, im right outside,  _ you said.

The tiny “seen” message popped up, but no reply. You waited several seconds before one of the lab doors edged open enough to show Mettaton’s uncovered eye, which stood out against his dark form, backlit by a faint blueish light.

“Hi,” you said innocuously, looking at him in confusion.

“Shh!” Mettaton slid the door open a bit more, squinting around as if he were a teenage boy sneaking his girlfriend in for a “sleepover.”

“Why do I have to ‘shh!’?” you asked in a quieter voice. The robot took your hand and guided you inside, making sure the door closed silently.

He caught you off guard when he swept you into his arms, and he cringed at your surprised cry. You felt his warmth as he leaned his face in close to you. 

“Look, Alphys is doing important work, and she made me promise to be quiet if I was going to stay here tonight.” Mettaton began to walk carefully over to the escalators, but you stared at him in shock.

“Then why are we doing this here?!” You scream-whispered. Mettaton was multitalented to say the least, but no matter what you tried, it was next to impossible for him to keep quiet during sex.

He loosed an uncharacteristic nervous laugh, intended to be playful but warped under the threat of your fury. “Sorry dear, but you were right. I was being a lazy-ass. But there’s always fun to be had with this kind of situation where you’re in danger of being walked in on, right?”

He would. You were rendered speechless, and you let your head hang over his arms in exasperation. He made it to the second floor and stepped off the escalator, turning towards a narrow hallway. He reached one of several doors, and then set you down.

“I don’t think I’ve ever gotten the chance to show you, but this is my room for when I stay overnight at the lab.” He tapped a glowing blue circle which was in place of a doorknob, and the door slid open, allowing you both inside.

It was smaller and more minimalist than you expected, but that was probably because he didn’t stay here that often. It was very dimly lit except for tiny strings of pink lights that lined the ceiling, which drew attention to a very comfortable-looking bed in the left corner.

Traipsing over to said bed, Mettaton settled on the mattress, throwing you that classic lusty stare while crossing his legs. “Now, this room isn’t much, but it certainly sets the mood, doesn’t it?”

“It does,” you agreed, your voice sounding a bit removed. A few seconds elapsed before you found yourself straddling him, your mouths meshed.

You deliberated on how to conduct the more dominant role you’d be playing, but it was hard to think straight with strong metal hands gripping your body while a resounding noise of pleasure passed from his mouth to yours. You decided to leave your actions up to feeling and not to overthink it, as your figured that might turn awkward. You felt Mettaton’s hand curl around yours, guiding it down.

“Here, take off my clothes for me,” he entreated, “I have a couple surprises for you.”

You stood at attention, dying to know what they were. “Other than the fact that you’re wearing your cock?” you asked jokingly, seeing the bulge in his leggings.

“Oh yes,” he said mischievously, allowing you to grab his waistband and peel off his skintight pants.

You gulped hard at what you saw, rushing to get the fabric completely off of him while, as usual, keeping his boots on. Hugging the swell of his hips were a pair of pink crotchless panties, perfectly skirting the base of his dick in a pretty lace trim. Mettaton pressed his fingers to the sensitive heart-shaped ridges on his underside, rubbing gently amidst a growing stream of slime oozing from his heart just above.

“Now, take off your clothes and I’ll show you the second surprise.”

You couldn’t have stripped any faster. All the while, you basked in his poise, so authoritative, yet so swamped with arousal that he couldn’t help but succumb to you, and he loved every second of feeling it.

Once you were naked, Mettaton moved further onto the bed, getting onto all fours for you. You blushed hard at how exposed he was, and how the view looked exactly the same as when you had walked in on him after his upgrades, except for one thing.

You burned with dirty excitement as he spread himself, proudly donning what you assumed was a buttplug with a fake gemstone for a base. Oh my god.

“I’ve been wearing this for half an hour, but it still feels so tight inside,” he said in a way that only worked you up even more. Unreservedly, you moved forward and put your hands on him, squeezing his thighs and cheeks with relish. He let out a small yelp that diffused into a moan, which was adorable.

“I’ll try to loosen you up a bit,” you said. You couldn’t help but lick your lips for half a second. Everything you’d been fantasizing about today was going to come true and you were going to make sure to have Mettaton delirious by the time you were finished.

You placed your thumb on the ridge of tender lavender skin surrounding the plug. It was warm and damp. “Do you self-lubricate from here, too?” You asked him.

“Mn, yes,” he breathed as you traced your finger around the plug. Your ministrations already had him squeezing his thighs together and clenching around the object inside him. You tried to resist touching yourself.

“It’s… also about as sensitive as my pussy,” he added coyly.

“Wow,” you said. A smack to his ass had him hissing blissfully. “Mett, that’s so slutty.”

“Says the one who gets off on being covered nearly head-to-toe in my slime,” he retorted. Oh, he was going to be a hell of a power bottom, and you were so ready.

“Let’s take this thing out,” you said. You pulled on the base of the plug, but even through the lubrication it took a bit of effort to pull out the larger part of it.

“You weren’t kidding when you said it was tight.” It was probably because it had just been installed, and hadn’t had a chance to stretch and flex yet. “Here, look at me,” you ordered once you had gotten it out.

Glancing at him filthily, you brought the plug to your mouth and sucked off the lube to test its flavor. Like his usual taste, but with a hint of something citrusy. You loved how his taste differed depending on which of his erogenous zones you licked.

“Fuck, darling,” he choked out as he watched you. “Just put your fingers in me. Or your tongue, I’m not picky, I just need to get looser,” he continued.

“Don’t have to tell me twice,” you said. You placed the plug on the side table near the bed. With a sly grin, you brought your fingers to his entrance and began massaging in circles to wetten them. He was still gaping a bit from the toy.

“Feels good?” you asked.

You could already hear the whirring of the fans in his chest. “Not as good as it’s going to feel, I’m sure,” he breathed.

You were determined to turn that into an understatement. Now your fingers were slippery enough to slide past the ring of artificial muscle, up to the knuckle.

Fingering his ass elicited such cute noises from him at the new sensation. The inside felt very authentic, too (you assumed, since you had never, er, fingered an ass before). This raised another question.

“Please tell me there’s a prostate in here somewhere.”

“I think the plug brushed up against it once or twice, Mettaton said, the glitching beginning to take hold of his voice.

“Hmm,” you mused, pumping your fingers a few more times and scissoring them for good measure. “It might be too far up to reach with my tongue, but let’s give it a shot anyway.”

He managed an enthusiastic utterance you couldn’t quite make out, coinciding with a vehicular rev of his fans. You allowed him a second to shove one of the pillows on the bed under his chest, putting him in a position that was easier to work with.

You wanted to appreciate the view, but you didn’t want to keep him waiting. Hooking your finger under his panties and snapping them, you bent over and pressed your mouth against his entrance.

“Mmm-m, fuck,” he whispered almost at once. He tilted his hips up closer to you, wriggling a bit to get the most stimulation possible. Of course he was craving it; he had two other very sensitive spots that weren’t receiving your attention.

“I’m gonna rub your heart a little bit while I do this, okay?” You told him softly.

“Please,” he trembled.

You sucked tenderly on him, and placing a finger on the dribbling surface of his soul, you plunged both your tongue and digits inside of his warmth.

You felt your face flush as you unfurled your tongue fully, letting it be swathed by that channel of muscle. It constricted around you amidst the robot’s dirty moans, and your crotch burned with need again. You tried to ignore that, but it was proving to be difficult. The most you could do was rub your thighs together at the slimy, wet noises that spurted out each time you moved your tongue around.

“F-feels so good,” you heard him keen. He jolted when you synchronized your fingers and tongue, and now his noises were bordering on too loud.

“I don’t know about you, Mett,” you said, after withdrawing your fluid-saturated mouth, “but I’d prefer it if I didn’t get weird looks from Alphys after we’re done here.”

Mettaton huffed at you. Instead of replying, he scooted his ass closer to you indignantly, wanting you to keep going. You decided to exercise your dominant status and push him onto his stomach, and then you grabbed his shoulder to turn him onto his back.

“That’s not a request,” you insisted.

“It’ll take a little more demanding than that to get me to be quiet since I don’t have a ball gag lying around,” he said smugly. Your composure was compromised when he took the chance to shove his thigh between your legs. You were so desperate to be touched that it pained you to push him away when he started rubbing against your cunt.

“Fine then,” you said. You raised your right hand and brought it down onto his heart. You made sure to press the entirety of your palm on it firmly, causing slime to stream out like water from a sponge. Mettaton made a choking noise, throwing his head back.

“If you don’t stay quiet,” you murmured, “I’ll just press on this until you can’t take it anymore.” You knew that at a certain point his soul could be crushed, and his life obliterated, but it required a strength _ far _ beyond yours to do any real damage. The most you were capable of was inflicting a moderate pain, which he enjoyed, but a constant pressure wasn’t enough to make him come.

“Or,” you considered, “I could also drop whatever I’m doing and just touch myself till I come if you can’t hold back your disgusting noises. Maybe I’ll detach your arms and hump your thighs, or your face. That way you have no choice but to watch me come without you.”

Mettaton’s expression was enough to reassure you that your topping abilities were competent. Maybe even more than competent, since you caught his dick twitch with arousal, and his visible eye roll languidly upwards. “Whatever you say, darling,” he moaned. “Or more appropriately,  _ master.” _

You didn’t expect that simple word to send an electrifying thrill down your spine, but it did. Fuck him in the ass, literally. In fact, immediately.

“That’s what I like to hear,” you smirked, hiding how flustered you were. “Now, where’s that strap-on you said you had?”

Mettaton’s eye lit up marvelously. Sitting up from the bed, he rolled over to face the side table and opened one of the drawers, rummaging around a little. He looked carnivorous as he drew out his chosen attachment, holding it like it was sacred as he handed it to you.

“Woah, I don’t think I’ve seen this one,” you remarked. You were actually impressed by how long it was. It must have been 12 or more inches in length, complete with a bulbous head and plenty of different-sized ridges.

“Well, I bought it in hopes that I could try it on you,” Mettaton explained. “You know, back before I got an attachment I could feel. But after we did it with a smaller strap-on I realized that using this one might practically impale you through the skull.”

“You think?” you chuckled. It was true that it looked like it could easily skewer your uterus and other neighboring organs, but it was perfect for him, a man of few fragile innards. To tell the truth, picturing him taking all sorts of huge dicks and toys with such enthusiasm was a common fantasy of yours. The fact that he had picked this one to use tonight made you very pleased.

“You’re really sure this won’t damage you, though?” you reiterated.

“Positive,” Mettaton insisted. “All we need to do is lube it up nicely.” He kissed your face quickly, now taking the straps of the toy in his hands to fasten it to you. Once he was done,  he moved back to look at you.

“Ah, it’s perfect, “ he gushed. “You look like a force to be reckoned with.”

You smiled at him, then looked down at yourself, amused by the contrast between your small body and the girth of that overly-knobby rod of silicone. The robot wrapped his hands around your attachment, leaning his face towards it.

“O-Oh, are you--”

“I’m sure you’ll get a kick out of watching this,” he purred. “No gag reflex.”

With that, he wrapped his plump lips around the tip of the cock, and gently eased the entire thing into his cavernous mouth. Your eyes widened when he reached the hilt without so much as a pause. He moaned wantonly, and the sound was muffled by the thickness of the toy, which was surely occupying his entire throat.

He pulled his head back, leaving the cock wet with a salivary film. Judging that it needed a bit more wetness, he clutched the base of the cock, brought his mouth close again, and flashed his eye up at you naughtily as he lapped at the head with the whole of his tongue.

“Fuck yes,” you blurted out. Without thinking, you clutched the back of his head as he bobbed down a second time. He didn’t mind in the slightest, growling in  pleasure at his hair being pulled.  He continued to suck hard and hungrily, and the sight almost gave you a phantom feeling in that chunk of plastic to make up for how neglected your pussy was. You felt your own fluids dripping down your thighs by now.

Once the toy was sufficiently soaked, Mettaton wasted no time in turning back around and offering himself to you again, spreading himself as wide as possible in his urgency.

“I can’t fucking wait any longer,” he wailed. “Put it in me, darling.”

“You think you can put that  _ more appropriately? _ ,” you asked audaciously, torturing him by gripping his hips with the toy only inches away.

He emitted a sudden loud mess of technologic fussing, which he wasn’t supposed to do. He quickly quieted down and rephrased his sentence.

“ _ Fill me up with your cock, master, _ ” he whined.

“Better.”

You positioned the head of the cock right at his entrance, and then carefully pushed in. Now that he had been somewhat loosened, it was an easier task than you had expected. Euphoria spilled from the robot’s mouth as the knotted surface of the cock rippled across the bands of his insides, and you could feel the reverberations because of how tight he still was. The attachment was pretty long, so you figured it wouldn’t be long before you found that g-spot he claimed to have.

You sped up a little more, and Mettaton’s hands clutched the sheets as he arched his back upwards. He seemed to be moving around to find that g-spot too, and you tried to help by changing your angle and the way you thrust your hips.

“Oh g-g-od,” he panted erratically. “Oh god, it’s-s so close,”

“Coming already?” you asked. You hoped he wasn’t, since you were just getting started with him.

“N-not quite,” he denied. “M-m-my fucking  _ ahh,  _ mm, my prostate, almost…”

He didn’t say anything else, but you understood that he was frantic with how just out of reach his g-spot was. Now he experimentally brought both knees near his chest, and you leaned over him, continuing to thrust. He cried out much too loudly.

“Yes, yes!” A lengthy spasm of his robotic voice. “Ah, faster,  _ please, right there,  _ I n-need you to slam int-to me!”

Your hips struck him harder, causing him to descend further into his elated frenzy. He was unable to quiet himself as you had instructed him, letting all sorts of pornographic expletives fly loose as if no one were in the lab. You decided something had to be done about that.

To Mettaton’s horror, you pulled out of him without hesitation. He shivered, punching the mattress weakly, but before he could start his caterwauling, you had him on his back again, looking extremely displeased.

“I don’t care if I’m being disobedient,” he bristled before you could say anything. “I deserve to have that cock in me anyway.”

You stared at him intently. “You’re gonna do what I say. And I said I would just come without you if you started acting up.” You looked sideways pensively to keep him on the edge. “But, since you are a star and all, I’m giving you a second chance.”

Mirroring what he normally did to you, you planted your hands on either side of him, staring down with an imminent look in your eyes. “Bite your lip this time, or I’ll really leave you blue-balled.”

You couldn’t help but break character for an instant, kissing him with a content smile.

“God, darling, the things you do to me,” Mettaton said under his breath..

The moment of respite didn’t last for long, since you had been waiting to get him in this position so you could watch him in his raptured fervor. He was delighted to be filled again, and you were delighted to see his face contort into every slutty expression imaginable. You picked up speed once more, and he was about to let out more disgraceful noises, but he remembered your warnings and smothered his moans, gnashing on his bottom lip.

“Mmm, oh,” he said, opening his mouth right after. “You’re h-hitting it again, mm…”

He shut up when you drew your hips almost all the way out, only to slam the cock back in. This sent Mettaton teetering on the edge, screaming silently, and you were close too, though your only stimulation was the shock from ramming into him. You weren’t being touched directly, yet you were a sweaty mess, you felt your heartbeat in your hands, and devouring the sweet, shameful mess that was the sight of the slime-covered robot only made you want to hump even faster.

You felt a firm sultriness close in around your pelvis, squeezing tight. He had wrapped his heavy thighs around you, a nonverbal plea for more pressure, more movement.

“Oh god,” you wailed. You were so close together that his heart slime splattered with every thrust, and his dick slapped against your lower belly, brimming with a need for release.

“Pl-lea-s-se!” Once he was past the point of coherence due to the fitful, digital-sounding vocal glitches, you knew he’d had his fill of waiting. Primal instinct drove your hips violently forward, madly seeking touch, and madly seeking Mettaton’s breaking point.

You had to push hard to sufficiently sate him through his impassioned orgasm, which made it a herculean task to keep completely silent. Even through his bit lip, he screeched and groaned with abandon, jerking his hips and clenching his ass at the abuse of his g-spot.

You thought your own climax was just out of reach, but you were proven wrong as you watched ropes of cum spurt from Mettaton’s dick and spatter all over himself, everything from his free-flowing heart, to his chestplate, to his depraved face being flecked with gooey essence. You catapulted into orgasm along with him, the pleasure welcomed but a bit uncomfortable and searing with nothing to directly frot against. Everything was a concert of exhausted moans and disgusting viscous sounds as the high plateaued and eventually subsided.

Your arms gave out, and you landed with a  _ splat  _ on Mettaton’s front, not bothering to take out the strap-on either. His internal fans chugged away in your ear for a small while until Mettaton came somewhat back to his senses.

“Did you come?” he asked

“Yeah,” you replied.

“Oh, that won’t do,” he said with worry. “It must’ve burnt to come untouched. I know the feeling.”

“It’s not a big deal,” you assured him.

He looked at you for a moment. “Here, come straddle my face so I can make up for that.”

Since you had recuperated for a few minutes, you weren’t hesitant to do this because of your own exhaustion. You were more concerned for him.

“I don’t want to overwork you, though,” you said.

“All I have to do is suck on your clit, nothing more,” Mettaton held. “I’m sure that’s what you want.”

You shivered a little at the thought of some honest-to-god stimulation. “Alright,” you accepted. “Let me just take this thing out.”

Mettaton shuddered and groaned when the large toy slipped out of him. You unfastened it from yourself, tossing it to the side of the bed. You lifted a leg over him and settled onto his face, letting your eyes close with satisfaction.

He sucked on you rhythmically, holding you down by the tops of your thighs until you came again. It wasn’t quite as intense, having been the second time around, but you still relished in the sensation, which was much better than none at all.

Once you were finished, Mettaton sat up with a hand to his mouth and a strange expression on his face.

“Bad day for eating out?” you said, starting to become embarrassed.

“Oh, no, no,” Mettaton denied. He pinched his bottom lip, feeling it tenderly. Realizing something, he laughed breathily to himself.

“What?”

“Babe,” he chuckled, “I chewed a hole through my lip. Bit right through the skin.”

“Really?” you said in disbelief. You got closer to him to see. He stretched his lip to show you, and you could see the small hole situated right on the border where the black of his lip met the white of his face.

“I didn’t even feel it,” he continued, laughing harder. “Looks like Alphys is going to know about this whether we like it or not.”

“I’m sure she knows already. You sucked at keeping quiet.”

“Well, no apologies in that department,” Mettaton said coyly.

You suddenly became aware of how messy the two of you were. Apparently, so did Mettaton, as he realized that he had come so hard there was robot semen on his face. He looked impressed at his own trajectory when he casually wiped it off with the tip of his finger and cleaned it with his mouth.

“Time for the fated post-coital cleanup,” you declared.

“And that it a task I am  _ not  _ up for,” Mettaton said stubbornly. Opening the drawer in his side table, he got out several hand towels and nothing more.

“Mett, hand towels are not gonna clean the massive splotch of sex glop from your bed.”

Shooting you a look, he opened a cabinet beneath the drawer and grabbed a beach towel, flicking it open and laying it over the mess. He used the hand towels to wipe down his body, offering you one as he did so. “It won’t hurt to let the laundry wait a bit,” he said. You took the towel, but noticed his actions becoming very sluggish. Soon enough he had given up on cleaning and lain on top of the large towel, looking completely lethargic.

“Are you shutting down?” you asked.

“Think...so,” the robot confirmed. “Charger…”

You followed his feeble pointing hand to the far corner of the room, where the familiar cable sat in a neat coil. As you fretted over plugging him into the nearby outlet, you caught him smile a dopey smile at you, his face illuminated cozily by the string of lights overhead.

A more innocent kind of blush crossed your cheeks at how peaceful and loving he looked in this state. You finally found his charging port, and hooked him up to the outlet, causing a small whirr to start up and a tiny yellow light to appear on the edge of his chassis.

“Thank you, darling,” he said gratefully.

“It’s no problem,” you murmured. You settled down next to him as he tugged on you arm, wanting you to come closer.

“Love you,” he whispered.

“I love you too, bolts-for-brains,” you said back, attempting to be lighthearted. After what you two had just done, a heartfelt interaction like this one shouldn't have flustered you so much, but it was anyway.

Mettaton, his battery depleted, went into sleep mode. You took a look in the cabinet where he had gotten the beach towel, and found another one to use as a blanket for the both of you since it was a bit chilly. The ambience of the room made you drowsy, and it was easy to drift off to sleep.

You were woken up a few minutes later by a knock on the door and a stuttering voice asking what Mettaton had been doing for the past half hour or so, but you dealt with the crushing mortification of Alphys discovering you both naked. The laundry was a pain to help out with, too. But suffering under these things with Mettaton by your side made the worst of it the best.

**Notes for the Chapter:**

> christ. ok. i dont wanna stop writing fic its fun but at the same time 1. it sucks up time i need for drawin and stuff and 2. mtt sexfests arent gonna be in demand forever lol!! so a very hesitant maybe on my possible next fic being uhhhhh im thinkin mettacest x reader?? not promising anything but the intention is there :9

**Author's Note:**

> so the usual 3 chapter smut format I seem to favor??? coolio 
> 
> cant wait to peg a robot


End file.
